I use a lot of technical terms and made-up abbreviations when I jot down notes in Stickies. This causes the spell checker to underline more or less every word in red, which is annoying. Luckily, there is a way to permanently disable spell checking, for all notes. In retrospect, it is really, really obvious how to do it, but it took me a while to figure it out.

First, make sure spell checking is disabled for the current note, using Edit » Spelling and Grammar » Check Spelling While Typing. Then, mark that note's settings as the default, using Note » Use as Default. (This will also set the note's color and font as the default.)

I don't think it's even remotely obvious, even after reading the explanation, but thanks for sharing this tip! I generally don't need a spell checker at all, and the inability to completely disable it (without hacking the OS) is very annoying. But at least I won't have to deal with the problem in Stickies anymore!

Note that this is for 10.6 only; in my testing, it had no effect in 10.4 or 10.5. However, for each older OS, what DID work was to follow the instructions in this older Unlock hidden features within Stickies hint (right-click on the Stickies app, click Show Package Contents, open Contents -> Resources -> English.lproj -> StickiesDocument.nib, select Tools > Inspector, click on the Stickies window, untick "Continuous Spell Checking" in the Inspector, and save). Every note you create from then on will have spell checking disabled by default.